Low-crest-factor multitone test signals for audio testing

Many frequency domain audio tests, such as measuring the frequency response, measuring frequency-dependent crosstalk, or making some kind of distortion measurements, can be performed by applying multitone test signals to the audio device under test and analyzing the output signal by means of the discrete Fourier transform. In contrast to standardized single-tone or dual-tone excitation tests, the multitone test offers significant time savings and enables realistic test conditions by approximating the frequency domain characteristics of a typical program material. But multitone testing requires the design of low-crest-factor test signals. Several computation schemes and indirect optimization methods of low-crest-factor phases, are discussed, and for the first time optimum multitone signals designed by general-purpose nonlinear optimization software are presented.